Create an infrastructure for parallel computation in PostgreSQL.

This does four basic things.  First, it provides convenience routines
to coordinate the startup and shutdown of parallel workers.  Second,
it synchronizes various pieces of state (e.g. GUCs, combo CID
mappings, transaction snapshot) from the parallel group leader to the
worker processes.  Third, it prohibits various operations that would
result in unsafe changes to that state while parallelism is active.
Finally, it propagates events that would result in an ErrorResponse,
NoticeResponse, or NotifyResponse message being sent to the client
from the parallel workers back to the master, from which they can then
be sent on to the client.

Robert Haas, Amit Kapila, Noah Misch, Rushabh Lathia, Jeevan Chalke.
Suggestions and review from Andres Freund, Heikki Linnakangas, Noah
Misch, Simon Riggs, Euler Taveira, and Jim Nasby.

1 files changed, 30 insertions, 0 deletions

diff --git a/src/backend/utils/adt/lockfuncs.c b/src/backend/utils/adt/lockfuncs.c
index a1967b6963..491824dd6b 100644
--- a/src/backend/utils/adt/lockfuncs.c
+++ b/src/backend/utils/adt/lockfuncs.c
@@ -13,6 +13,7 @@
 #include "postgres.h"
 
 #include "access/htup_details.h"
+#include "access/xact.h"
 #include "catalog/pg_type.h"
 #include "funcapi.h"
 #include "miscadmin.h"
@@ -411,6 +412,15 @@ pg_lock_status(PG_FUNCTION_ARGS)
 #define SET_LOCKTAG_INT32(tag, key1, key2) \
 	SET_LOCKTAG_ADVISORY(tag, MyDatabaseId, key1, key2, 2)
 
+static void
+PreventAdvisoryLocksInParallelMode(void)
+{
+	if (IsInParallelMode())
+		ereport(ERROR,
+				(errcode(ERRCODE_INVALID_TRANSACTION_STATE),
+				 errmsg("cannot use advisory locks during a parallel operation")));
+}
+
 /*
  * pg_advisory_lock(int8) - acquire exclusive lock on an int8 key
  */
@@ -420,6 +430,7 @@ pg_advisory_lock_int8(PG_FUNCTION_ARGS)
 	int64		key = PG_GETARG_INT64(0);
 	LOCKTAG		tag;
 
+	PreventAdvisoryLocksInParallelMode();
 	SET_LOCKTAG_INT64(tag, key);
 
 	(void) LockAcquire(&tag, ExclusiveLock, true, false);
@@ -437,6 +448,7 @@ pg_advisory_xact_lock_int8(PG_FUNCTION_ARGS)
 	int64		key = PG_GETARG_INT64(0);
 	LOCKTAG		tag;
 
+	PreventAdvisoryLocksInParallelMode();
 	SET_LOCKTAG_INT64(tag, key);
 
 	(void) LockAcquire(&tag, ExclusiveLock, false, false);
@@ -453,6 +465,7 @@ pg_advisory_lock_shared_int8(PG_FUNCTION_ARGS)
 	int64		key = PG_GETARG_INT64(0);
 	LOCKTAG		tag;
 
+	PreventAdvisoryLocksInParallelMode();
 	SET_LOCKTAG_INT64(tag, key);
 
 	(void) LockAcquire(&tag, ShareLock, true, false);
@@ -470,6 +483,7 @@ pg_advisory_xact_lock_shared_int8(PG_FUNCTION_ARGS)
 	int64		key = PG_GETARG_INT64(0);
 	LOCKTAG		tag;
 
+	PreventAdvisoryLocksInParallelMode();
 	SET_LOCKTAG_INT64(tag, key);
 
 	(void) LockAcquire(&tag, ShareLock, false, false);
@@ -489,6 +503,7 @@ pg_try_advisory_lock_int8(PG_FUNCTION_ARGS)
 	LOCKTAG		tag;
 	LockAcquireResult res;
 
+	PreventAdvisoryLocksInParallelMode();
 	SET_LOCKTAG_INT64(tag, key);
 
 	res = LockAcquire(&tag, ExclusiveLock, true, true);
@@ -509,6 +524,7 @@ pg_try_advisory_xact_lock_int8(PG_FUNCTION_ARGS)
 	LOCKTAG		tag;
 	LockAcquireResult res;
 
+	PreventAdvisoryLocksInParallelMode();
 	SET_LOCKTAG_INT64(tag, key);
 
 	res = LockAcquire(&tag, ExclusiveLock, false, true);
@@ -528,6 +544,7 @@ pg_try_advisory_lock_shared_int8(PG_FUNCTION_ARGS)
 	LOCKTAG		tag;
 	LockAcquireResult res;
 
+	PreventAdvisoryLocksInParallelMode();
 	SET_LOCKTAG_INT64(tag, key);
 
 	res = LockAcquire(&tag, ShareLock, true, true);
@@ -548,6 +565,7 @@ pg_try_advisory_xact_lock_shared_int8(PG_FUNCTION_ARGS)
 	LOCKTAG		tag;
 	LockAcquireResult res;
 
+	PreventAdvisoryLocksInParallelMode();
 	SET_LOCKTAG_INT64(tag, key);
 
 	res = LockAcquire(&tag, ShareLock, false, true);
@@ -567,6 +585,7 @@ pg_advisory_unlock_int8(PG_FUNCTION_ARGS)
 	LOCKTAG		tag;
 	bool		res;
 
+	PreventAdvisoryLocksInParallelMode();
 	SET_LOCKTAG_INT64(tag, key);
 
 	res = LockRelease(&tag, ExclusiveLock, true);
@@ -586,6 +605,7 @@ pg_advisory_unlock_shared_int8(PG_FUNCTION_ARGS)
 	LOCKTAG		tag;
 	bool		res;
 
+	PreventAdvisoryLocksInParallelMode();
 	SET_LOCKTAG_INT64(tag, key);
 
 	res = LockRelease(&tag, ShareLock, true);
@@ -603,6 +623,7 @@ pg_advisory_lock_int4(PG_FUNCTION_ARGS)
 	int32		key2 = PG_GETARG_INT32(1);
 	LOCKTAG		tag;
 
+	PreventAdvisoryLocksInParallelMode();
 	SET_LOCKTAG_INT32(tag, key1, key2);
 
 	(void) LockAcquire(&tag, ExclusiveLock, true, false);
@@ -621,6 +642,7 @@ pg_advisory_xact_lock_int4(PG_FUNCTION_ARGS)
 	int32		key2 = PG_GETARG_INT32(1);
 	LOCKTAG		tag;
 
+	PreventAdvisoryLocksInParallelMode();
 	SET_LOCKTAG_INT32(tag, key1, key2);
 
 	(void) LockAcquire(&tag, ExclusiveLock, false, false);
@@ -638,6 +660,7 @@ pg_advisory_lock_shared_int4(PG_FUNCTION_ARGS)
 	int32		key2 = PG_GETARG_INT32(1);
 	LOCKTAG		tag;
 
+	PreventAdvisoryLocksInParallelMode();
 	SET_LOCKTAG_INT32(tag, key1, key2);
 
 	(void) LockAcquire(&tag, ShareLock, true, false);
@@ -656,6 +679,7 @@ pg_advisory_xact_lock_shared_int4(PG_FUNCTION_ARGS)
 	int32		key2 = PG_GETARG_INT32(1);
 	LOCKTAG		tag;
 
+	PreventAdvisoryLocksInParallelMode();
 	SET_LOCKTAG_INT32(tag, key1, key2);
 
 	(void) LockAcquire(&tag, ShareLock, false, false);
@@ -676,6 +700,7 @@ pg_try_advisory_lock_int4(PG_FUNCTION_ARGS)
 	LOCKTAG		tag;
 	LockAcquireResult res;
 
+	PreventAdvisoryLocksInParallelMode();
 	SET_LOCKTAG_INT32(tag, key1, key2);
 
 	res = LockAcquire(&tag, ExclusiveLock, true, true);
@@ -697,6 +722,7 @@ pg_try_advisory_xact_lock_int4(PG_FUNCTION_ARGS)
 	LOCKTAG		tag;
 	LockAcquireResult res;
 
+	PreventAdvisoryLocksInParallelMode();
 	SET_LOCKTAG_INT32(tag, key1, key2);
 
 	res = LockAcquire(&tag, ExclusiveLock, false, true);
@@ -717,6 +743,7 @@ pg_try_advisory_lock_shared_int4(PG_FUNCTION_ARGS)
 	LOCKTAG		tag;
 	LockAcquireResult res;
 
+	PreventAdvisoryLocksInParallelMode();
 	SET_LOCKTAG_INT32(tag, key1, key2);
 
 	res = LockAcquire(&tag, ShareLock, true, true);
@@ -738,6 +765,7 @@ pg_try_advisory_xact_lock_shared_int4(PG_FUNCTION_ARGS)
 	LOCKTAG		tag;
 	LockAcquireResult res;
 
+	PreventAdvisoryLocksInParallelMode();
 	SET_LOCKTAG_INT32(tag, key1, key2);
 
 	res = LockAcquire(&tag, ShareLock, false, true);
@@ -758,6 +786,7 @@ pg_advisory_unlock_int4(PG_FUNCTION_ARGS)
 	LOCKTAG		tag;
 	bool		res;
 
+	PreventAdvisoryLocksInParallelMode();
 	SET_LOCKTAG_INT32(tag, key1, key2);
 
 	res = LockRelease(&tag, ExclusiveLock, true);
@@ -778,6 +807,7 @@ pg_advisory_unlock_shared_int4(PG_FUNCTION_ARGS)
 	LOCKTAG		tag;
 	bool		res;
 
+	PreventAdvisoryLocksInParallelMode();
 	SET_LOCKTAG_INT32(tag, key1, key2);
 
 	res = LockRelease(&tag, ShareLock, true);